SIR: In a recent British survey more than a quarter of cows' milk samples tested had levels of organochlorines above the Maximum Residue Level and must therefore be considered to be a risk to the consumer. Information from the US Centre for Disease Control states that seizures have occurred in people who consumed food contaminated with an organochlorine pesticide at levels well below that previously thought capable of inducing seizures.

According to the Epilepsy Information Service, laboratory research in Europe and the USA suggests that repeated low-level exposure to organochlorines can increase susceptibility to seizures. This may occur as a result of the interaction between organochlorine pesticides and neurotransmission within the central nervous system. Acute exposure to the organochlorine lindane can cause convulsions.

If you wish to reduce your intake of pesticide residues in food the Soil Association Organic Symbol denotes pesticide-free farming practices. When buying chemicals, especially those which may contain organochlorines such as wood preservatives, print solvents and insecticides, the CHIPS (Chemical Hazards) information sheet which is available from retailers gives product details no longer available on packaging.

Ms F Kelly, Wray Close

Ashurst Wood, Sussex

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